It is known that a conventional storage system has a system called “RUS (Replication Utility for SyncImage [trademark])” having a function that copies file data to a remote place. This system is called a “remote replication” system or “remote copy” system. This is a system for performing remote copying from a NAS unit at a local site via an IP network to a NAS unit at a remote site.
The unit at the local site creates a virtual file system as a snapshot and stores differential information as a result of data update, thereby enabling users to obtain backups of a plurality of generations.
Creation of snapshots at a NAS unit is disclosed in Japanese Patent Laid-Open (Kokai) Application Publication No. 2004-342050. The NAS unit provides users with data images staticized at the time of acquisition of a snapshot of a primary volume as an operation volume which is continuously accessed by a client computer, based on the primary volume and a differential volume storing data before update when the primary volume has been updated.
As the local site copies differential data between snapshot generations to the remote site, the remote site can always provide users with remote backups of operation volume file data at the local site at a certain point in time.
If the storage system is to start the operation to perform remote copying between the local site and the remote site, an administrator or an operator of the storage system needs to execute a pair definition between a primary volume at the local site and a replication volume at the remote site on the units at both sites and copy the entire data of the primary volume to the replication volume. This is called “initial copying.”
Other conventional arts related to the present invention include Japanese Patent Laid-Open (Kokai) Application Publications Nos. 2007-241848, 2008-129723, 2007-317186, and H11-102262.